For the contributions where the Larin prescription have been used, an
additional \(\overline{\mathrm {MS}}\)  renormalization constant has to be taken
into account. An axial-vector current treated with the Larin prescription
must be renormalized with the factor [1]}, [2]}
\(Z_A &= 1+ \left(\frac{{\alpha _s}}{\pi }\right)^2\frac{1}{\epsilon }\biggl (\frac{11}{24} C_A C_F-\frac{1}{6} C_F T_F n_f\biggr )+ \left(\frac{{\alpha _s}}{\pi }\right)^3\biggl [\frac{1}{\epsilon ^2}\biggl (-\frac{121}{432} C_A^2 C_F+\frac{11}{54} C_A C_F T_F n_f\nonumber \\ &-\frac{1}{27} C_F T_F^2 n_f^2\biggr )+\frac{1}{\epsilon }\biggl (\frac{1789}{2592} C_A^2 C_F-\frac{77}{144} C_A C_F^2-\frac{26}{81} C_A C_F n_f T_F+\frac{1}{9} C_F^2 T_F n_f\nonumber \\ &+\frac{1}{162} C_F T_F^2 n_f^2\biggr )\biggr ],\) 
